Blades or vanes for fluid flow machines

ABSTRACT

A variable geometry blade or vane particularly for use in a gas turbine engine comprises a rigid spine, a thin flexible sheet shaped to form the aerodynamic surface of the nose or tail of the blade, and actuation means adapted to move the sheet relative to the spine to vary the blade camber.

States Patent John 111. Ellinger Mickleover, Derby, England 855,668

Sept. 5, 1969 Oct. 19, 1971 Rolls Royce Limited Derby, England Sept. 12,11968 Great Britain Inventor App]. No. Filed Patented Assignee PriorityBLADES 0R VANES FOR FLUID FLOW MACHINES 7 Claims, 3 Drawing Figs.

user. 416/23, 4l6/l32,416/158,416/24O m. m F01d 7/00 Field of Search416/23, 24, 132, 240, 84, 15s

[56] References Cited] UNITED STATES PATENTS 2,616,509 11/1952 Thomas416/84 2,967,573 1/1961 Johnson 416/84 3,042,371 7/1962 Fanti 416/226 X3,158,338 11/1964 Cushman 416/84X FOREIGN PATENTS 100,913 9/1925 Austria416/240 961,742 4/1957 Germany 416/240 Primary Examiner-Everette A.Powell, Jr. Attorney-Cushman, Darby & Cushman ABSTRACT: A variablegeometry blade or vane particularly for use in a gas turbine enginecomprises a rigid spine, a thin flexible sheet shaped to form theaerodynamic surface of the nose or tail of the blade, and actuationmeans adapted to move the sheet relative to the spine to vary the bladecamber,

PATENTEDUET 19 197i Inventor Joy/v JZE 14/4/655' Attorneys BLADES RVANES FOR FLUID FLOW MACHINES This invention relates to a blade or vanefor use in a fluid flow machine such as a gas turbine engine.

Particularly when considering the vanes of gas turbine engines there areconsiderable advantages to be gained by providing some form of variationof the camber of the blades. However, this is difficult to achievereliably, and may particularly be so where the vanes are subject toconditions promoting vibrations and are structural members in additionto carrying aerodynamic loads. Such a case, for instance arises wherethe vanes form a spoked structure which carries a bearing.

The present invention provides a blade or vane which can be used tocarry loads other than it aerodynamic loads while being enable to varyits camber in response to variation of flight condition.

According to the present invention a blade or vane for use in a fluidflow machine comprises a rigid spine, a thin flexible sheet shaped toform the aerodynamic surface of either the nose or the tail of theblade, and actuation means whereby the sheet may be moved so as to varythe camber of the blade.

Preferably said sheet is attached to one flank of the blade and extendsto the other flank, and said actuation means preferably move thatportion of the sheet on said other flank substantially in the directionof the mean chord line of the blade.

Said actuation means preferably comprise a plurality of hydraulicbellows which act on the extremity of the sheet.

Said spine may extend into the hollow of said formed sheet, andadditional actuation means may be provided in the form of a plurality oftubular members lodged between the spine and the sheet and adapted to beinflated with foam or the like.

Preferably inextensible ties extend from one flank portion of the formedsheet to the other flank portion.

The present invention will now be particularly described merely by wayof example with reference to the accompanying drawings in which:

FIG. 1 is a partly broken away side elevation of a gas turbine enginecomprising blades according to the present invention,

FIG. 2 is a perspective and partly broken away view of a single bladefrom the engine of FIG. 1 and according to the present invention, and

FIG. 3 is a transverse section through the blade of FIG. 2. FIG. 1 showsa gas turbine engine comprising a main gas generator section 11 and afan 12. The fan comprises a plurality of rotor blades 13 which rotatewithin a cowling 14, the cowling 14 being attached to fixed structure ofan aircraft (not shown). The gas generator section 11 is carried fromthe cowl 14 by way of a plurality of stator blades 15 which extendbetween the cowl and the'gas generator in radially extending array andwhich perform the dual purpose of providing mechanical support for thegenerator section and acting as outlet guide vanes for the fan 12.

It will be appreciated that should some catastrophic failure occur suchfor instance as a bird strike destroying some of the blades 13, it wouldbe possible to considerably reduce the otherwise inescapablewind-milling drag of the engine by varying the camber of the stators 15.As explained below with reference to FIGS. 2 and 3 this possibility iscarried into effect by the present invention.

FIG. 2 is a perspective view of one of the blades 15. Each blade 15comprises a spine portion 16 of solid metal which comprises the centralportion of the blade and which also forms the rear sections of bothflanks of the blade. This spine is designed to be of sufficientmechanical strength to carry out the mechanical requirement of the bladeand shaped at the nose end to the profile of one blade surface in eachextreme position. Surrounding the nose portion of the spine 16 there isa thin sheet member 17 which comprises a thin sheet of metal bent toform a substantially hairpin section and which forms the forwardaerodynamic surfaces of the blade. This member 17 is attached to theconvex flank of the blade at 18 and extends from there to form the noseof the blade, doubles back on itself at the nose and extends along theconcave flank of the blade to a position approximately halfway alongthis flank at 19. The attachment at 18 is rigid; the attachment at 19 ismade by way of actuation means described below.

To stiffen the member 17 and to constrain its movement into an aerofoilshape under all its working conditions a plurality of cross ties 20 and21 are provided. These ties extend between the opposite flanks of theblade formed by the member 17 and pass through slots formed in the spine16. it will be appreciated that the ties prevent any considerabledeformation of the surfaces of the member 16 away from their aerodynamicshape. The ties are attached to the interior of the member 17 by weldingor a similar process, but in any case the ties are nicked at theirattachment to the interior of the member so that they tend to hinge atthese points rather than bending over their complete length andconsequently distorting the surface of member 17.

Actuation means are provided to move the member 17 to vary its positionand hence to vary the camber of the blade. These actuation meanscomprise several sets of pistons. The main set of pistons comprises aplurality of bellows 22 which are embedded within the spine 16 and whichare designed as compression springs extruded by oil pressure and formedso as to fail-safe with the member 17 in its normal position. Thebellows are arranged along the radial extent of the blade and extend ina direction substantially tangential to the blade surface at theposition 19, that is substantially parallel to the mean chord line ofthe blade. The bellows 22 are provided with pressure fluid from apressure line 23 which extends throughout the length of the blade from asupply of fluid pressure (not shown).

Each of the bellows 22 actuates the member 17 by way of a spring link24. In this way the free end of the member 17 may be moved over thedistance of operation of the bellows 22. It will be appreciated thatwith the bellows 22 in their fully retracted position the member 17forms a blade section of relatively high curvature (shown in dottedlines at 2613). In

this position the spine 16 and the member 17 abut precisely so thatthere is no significant discontinuity at 19.

it is required to reduce the camber of the blades the pistons 22 areactuated, pushing the member 17 into its condition of less curvature(shown at 26A). In this condition there will be a discontinuity at 19,but since this condition is in any case likely to be an emergencyposition, the small loss produced by this step is not of criticalimportance.

The bellows 22 form the main actuating means for variation of the shapeof the member 17, but in order to preclude vibration and extraneousmovement of the member 17 further locking means are provided which takethe form of a plurality of bellows 25 extending longitudinally of theblade and inter posed in the space between the forward part of the spine16 and the internal surface of the member 17. These bellows areconnected to a plurality of supply lines 27 extending within the spine16 to a supply (not shown) of compressed air and plastic foam. In usetherefore the set of bellows 25 on one side of the spine 15 is inflatedwith the air foam mixture for a particular position of the member 17,thus providing a leverage on the flank of the member 17 to retain it inits required position while the plastic foam helps to damp outaerodynamic induced vibrations which might otherwise occur within thebe]- lows 25. It will be appreciated that the nearest set of bellows inthe diagram is inflated when the member 17 takes up its position at 268of greatest camber while the distant set of bellows is inflated when themember is in its position 26A.

In operation both types of actuating means would be operatedsimultaneously, the bellows 22 controlling the rate of movement againstthe more compressible foam filled bellows 25. The curvatures of themember 17 at the two extremes of movement are defined by one of the twoforward sides of the spine 16 and the length of the links 20,. 21.Although the curvature along the radial extent of the blade remainsconstant, any required twist may be incorporated by sloping of themember 17 if the axial flow permits this.

It will be appreciated that this mechanism is best suited for relativelyfew and thick blades which require small angular movement, thus givingspines having maximum strength and reducing the cost of the mechanism.

Various modifications to the above embodiment would be quite feasible.Thus although in the above example the leading edge of the blade hasbeen made variable it would be possible to vary the camber of thetrailing edge of the blade either along or in conjunction with thevariable leading edge. Again certain parts of the actuation mechanismcould be removed or replaced by alternative mechanisms. The stiffnessand geometry of the attachment of the ties 20, 21 can be designed toalter the shape of the blade.

I claim:

1. A composite variable camber airfoil-shaped blade or vane for use in afluid flow machine, said blade or vane having two aerodynamic flanksurfaces with at least one of said flank surfaces being convex and saidblade or vane comprising:

a rigid spanwise spine member shaped to have at least a portion definetwo surfaces which respectively form at least a part of said twoaerodynamic flank surfaces and one spanwise end portion of the blade orvane;

a thin flexible sheet member shaped to define the other spanwise endportion of the blade or vane and having inner surfaces and outersurfaces with the outer surfaces providing continuations of said twosurfaces of said spine member and to define remaining portions of saidtwo aerodynamic flank surfaces, said sheet member having one spanwiseedge rigidly attached to one of said two surfaces of said spine memberto provide a rigid connection and its other spanwise edge lyingsubstantially flush with the otherof said two surfaces of said spinemember for relative movement with respect thereto;

actuation means operatively connected adjacent to said last-mentionedspanwise edge above said sheet member for moving the same relative tosaid spine member in a direction of a mean chord of the blade or vane tovary camber; and

rigid means extending between said innersurfaces of said sheet memberfor maintaining shape of said sheet member when said actuation means isoperated to vary camber 2. A blade or vane as claimed in claim 1 inwhich said actuation means includes a plurality of hydraulic bellows.

3. A blade or vane as claimed in claim 1 in which said rigid meansincludes a plurality of inextensible tie members extend ing between andfixedly attached to said inner surfaces of said sheet member.

4. A blade or vane as claimed in claim 1 in which said rigid connectionis on said convex flank surface of the blade or vane.

5. A blade or vane as claimed in claim 2 and in which said hydraulicbellows comprise compression springs adapted to move said sheet memberto a predetermined position should the supply of fluid to the bellowsfail.

6. A blade or vane as claimed in claim 1 and comprising additionalactuation means which comprise a plurality of tubular, inflatablemembers lodged between the spine member and the sheet member.

7. A blade or vane as claimed in claim 3 and in which said tie membercomprise weakened portions adjacent to their attachment to the sheetmember so that hinging is allowed at said portions.

1. A composite variable camber airfoil-shaped blade or vane for use in afluid flow machine, said blade or vane having two aerodynamic flanksurfaces with at least one of said flank surfaces being convex and saidblade or vane comprising: a rigid spanwise spine member shaped to haveat least a portion define two surfaces which respectively form at leasta part of said two aerodynamic flank surfaces and one spanwise endportion of the blade or vane; a thin flexible sheet member shaped todefine the other spanwise end portion of the blade or vane and havinginner surfaces and outer surfaces with the outer surfaces providingcontinuations of said two surfaces of said spine member and to defineremaining portions of said two aerodynamic flank surfaces, said sheetmember having one spanwise edge rigidly attached to one of said twosurfaces of said spine member to provide a rigid connection and itsother spanwise edge lying substantially flush with the other of said twosurfaces of said spine member for relative movement with respectthereto; actuation means operatively connected adjacent to saidlastmentioned spanwise edge above said sheet member for moving the samerelative to said spine member in a direction of a mean chord of theblade or vane to vary camber; and rigid means extending between saidinner surfaces of said sheet member for maintaining shape of said sheetmember when said actuation means is operated to vary camber
 2. A bladeor vane as claimed in claim 1 in which said actuation means includes aplurality of hydraulic bellows.
 3. A blade or vane as claimed in claim 1in which said rigid means includes a plurality of inextensible tiemembers extending between and fixedly attached to said inner surfaces ofsaid sheet member.
 4. A blade or vane as claimed in claim 1 in whichsaid rigid connection is on said convex flank surface of the blade orvane.
 5. A blade or vane as claimed in claim 2 and in which saidhydraulic bellows comprise comPression springs adapted to move saidsheet member to a predetermined position should the supply of fluid tothe bellows fail.
 6. A blade or vane as claimed in claim 1 andcomprising additional actuation means which comprise a plurality oftubular, inflatable members lodged between the spine member and thesheet member.
 7. A blade or vane as claimed in claim 3 and in which saidtie member comprise weakened portions adjacent to their attachment tothe sheet member so that hinging is allowed at said portions.